536 AD and all that

“during this year a most dread portent took place. For the sun gave forth its light without brightness… and it seemed exceedingly like the sun in eclipse, for the beams it shed were not clear.”

This quote from Procopius of Caesarea is matched by other sources from around the world pointing to something – often described as a ‘dry fog’ – and accompanied by a cold summer, crop failures and a host of other problems. There’s been a TV special, books and much newsprint speculating on its cause – volcanoes, comets and other catastrophes have been suggested. But this week there comes a new paper in GRL (Larsen et al, 2008) which may provide a definitive answer….

It’s long been known that tree-rings (such as the one pictured from Arizona) often show an extremely small growth ring for AD 536 (you can count back from the marked AD 550 ring). In fact, if you look at the mean anomaly in a whole range of tree ring constructions, this event stands out along with 1601 and 1815 (known volcanic events) as being exceptional over the last 2000 years.

Average of the high-frequency components of 7 northern European tree ring reconstructions from Larsen et al, 2008. The filtering ensures that uncertainties in long term trends (which are not important in this context) don’t confuse the issue.

These data match the written sources quite well. However, tying it to a cause has always been plagued with problems of chronology. An initial attempt to tie this event to a volcanic pulse in the Dye3 ice core in Greenland foundered when the chronology was revised to put it 20 years earlier. However, there has recently been a concerted effort to place all the Greenland ice cores on a common timescale based on annual layer counts (Vintner et al, 2006). Because all the cores are being counted together, ambiguities in one can be corrected by reference to the others. Once the dates have been better established, the sulphate records (which generally show the impact of volcanic aerosols) can be examined to see if they line up. And low and behold, they do:

The second peak in the picture is dated at 534 AD which is close enough to 536 AD given the one or two year uncertainty in counting. Note that the 534 AD peak is actually smaller than the one a few years earlier. In assessing the importance of an eruption though, it isn’t enough to have just a peak in Greenland. That could simply signify an eruption that was close by. Instead, people look for a matching peak in Antarctica. This signifies that the eruption was likely tropical and the aerosols were carried into both hemispheres by the stratospheric circulation. Here is where previous attempts often faltered. The dating of ice cores in Antarctica is less exact than in Greenland because the accumulation is slower (it doesn’t snow as much). However, the relatively new Dronning Maud Land (DML) core has comparable resolution to the Greenland ones, and this one does have a clear sulphate peak at about 542 +/- 17 years. That is good enough to be a match to the 536 AD peak in Greenland. The correction you’d need to make to align them exactly would also fix some other apparent offsets for smaller events in the subsequent 100 years.

So it probably was a volcano, somewhere in the tropics, and it was likely the size of Tambora in 1815. There has been some speculation that it was an earlier eruption of Krakatoa (which went off again in 1883), but that is uncertain, as are the numerous consequences such as the fall of the Rome or the rise of Islam which have been attributed to this event. While not exploring that too deeply, this quote from Michael the Syrian indicates dramatically the potential for climate events like this one to really spoil your day:

“The sun was dark and its darkness lasted for eighteen months; each day it shone for about four hours; and still this light was only a feeble shadow … the fruits did not ripen and the wine tasted like sour grapes.”

I am sure everyone has read Sir James Lovelock’s recent interview in the March 1 edition of the Guardian in the UK, written by Decca Aitkenhead, but if somehow you missed it, it is a must-read and also NSFW:

That event was quite large and also appeared to have resulted in a rather large climate impact. The historical information from China suggests major crop failures and famine. One of the interesting aspects of this report was the differences in dates for an event which might be considered well dated in historical records, even though there were no reports from the actual location.

I’ve also seen references to an event dated at 1259 CE, for which, last I heard, the location had not been determined. Apparently, the Baffin Island data places this event at a somewhat later date.

This event is well known from the long bristlecone record as well. For those interested in a good treatment of volcanism over the last 50 centuries should look to a paper by Salzer and Hughes last year in QR. Here.

Here is what they have to say on the subject:

There has been some suggestion that the AD 536 dust-veil event might be the result of a comet impact, however, rather than a volcano (Baillie, 1994). The AD 536–547 environmental disruption has been observed in multiple proxies and has been characterized as a widespread catastrophic event (D’Arrigo et al., 2001).

The improved dating of the ice core records via the layers is crucial for zeroing in on these large global events. I’m glad to see that this is moving forward.

And so another one bites the dust. :) IIRC the cooling related to this event has been used as the main benchmark separating the “Roman Warm Period” from the later “Medieval Warm Period,” which in the absence of enough data on vulcanism were imputed largely to inferred variations in solar irradiance along with various other minor climate regimes of the last few thousand years.

What’s interesting is how little attention this recent shift in the science has gotten (to the point that I for one had more or less missed it, although it was right there in the AR4 WG1 report).

I would not rely on my memory, but there are 2 events that may be related. One is an asteroid impact that wiped out a city in the ancient world and the other was a volcano on an island in the eastern Mediterranean. The asteroid was in something by John Lewis, maybe his book, “Mining the Sky,” but I’m not sure. I hope this helps your search.

There is an excellent book by historian David Keys, who covers the global consequences of this volcanic event. It is called “Catastrophe: An Investigation into the Origins of the Modern World”. (Published in 2000.)

Re #3, Ah what a nice picture he paints Mr Lovelock but his statements are starting to sound like the alarm bells that James Hansen is sounding. Mr Hansen as director of GISS (realclimates boss I believe)has recently in january 2008 started issuing warnings of safe limits for CO2 of 350 ppmv which is of course impossible to achieve in the present global economic economy, well unless we can mobilise ourselves to a level of magnitude that dwarves the second world war mobilisation. Oil copanies are not going to stop providing and producing oil, nor are coal companies coal or gas copanies gas but strategic targets by governments could be set but not 120% of CO2 reductions by 2020/2030 as is being requested here.

Hansen states that new paleoclimatic evidence leads him to believe that this is teh case and that 450 ppmv is an absolute upper limit but one that coms with enourmous consequences such as desertification and areas of uninhabiatability across the globe. Maybe Lovelock is right, be prepared to adapt for technology can be devised to do that rather than mitigate CO2 emissions as we can start from a clean slate. Build nuclear power plants to provide the adaptation energy to power the technology. Huge swathes of lans will be under water and food will probably need to be synthesized within 20 years.

It is all very apocolyptic and very doomey but as it comes from these two then I would suggest that we had better start listening. Science is very conservative and very skeptical and when it comes to AGW, it may not have shouted loud enough long enough.

So without derailing the conversation on the actual topic, what is the prevailing opinion on Lovelock and his current thinking? I’m asking from my position as a layman on the topic of Global Warming. Is he out there? Is he the extreme opinion? Or is there some truth to what he says? This is the second article I have read about Lovelock in the last couple of months, and just wondering how much of what he says is informed science, and how much is not?

Sigh! There’s still the odd skeptic in the woodpile I see. I’m afraid you lot are becomming increasingly ‘ODDer’ and rarefied…reason…The OVERWHELMING information that ‘PROVES’ ACC is happening. These are the world’s top, most repected scientists, each one experts and masters in their respective fields..each one has spent the best part of thier lives in the quest to understand how their chosen aspects of science works and interrelates to the other earth sciences. These silly little sceptics armed with all their weath of imaginary intelligence and doctorates seem to think that ALL these brilliant and searching minds have it ALL wrong..why dont you take a long hard look in a mirror so you can see how stupid and ridiculous you sound. I bet you dont work in highrise buildings either because some ‘expert’ of an architect built them and so with just the right wind speed and precipitation and relative humidity etc. they could suddenly come crashing down. So stop advertising your abject ignorance and actually listen to what the IPCC is telling you and accept the consequence that raising the most important greenhouse gas by 30%+ in the relative blink of an eye is having on our climate.

Without commenting on whether Lovelock’s assessment is correct in its various aspects, I am most struck by the logical inconsistency in his message.

On the one hand he states, “Global warming has passed the tipping point, and catastrophe is unstoppable.” As a consequence of that assessment he dismisses ideas such as renewable energy, recycling, avoiding flying etc. as pointless.

And yet, he strongly advocates using nuclear power as something that “can solve our energy problem.”

Well, why is saving CO2 emissions by using nuclear power important, but saving emissions by other methods a waste of time because it is already too late?

Such an inconsistency, it seems to me, renders his message incoherent.

PS. Sorry this is off topic. I did enjoy the 536AD tale, but then got distracted by #3!

There is nothing we can do! If I change all my light bulbs to low energy ones, will that save the world? If I sell my car and get a bicycle will that do? What if you join me, can we save the world together? I think not. Even if all the sensible people in the world stopped wasting energy, there is still another 90% who would go on driving the SUVs, jet skis, and monster trucks. Apart from macho men, how are the few remaining housewives going to get the food to feed their families? They need their car to take them to the supermarket to fetch the groceries.

Our only hope is that the next president of the USA will organise the world to take action. But any presidential candidate who advocates the actions needed will never get elected.

Let’s face it, GWB admitted that the USA is hooked on oil. Our only hope is if we (USA, UK, Europe, China, India, etc.) go cold turkey. Can you see that? Can you see any of the main three (good) candiates advocating that. Can you see them implementing it?

Lovelock’s advice was to enjoy yourself while you can. Why should it be that those who are destroying the world should be the ones to have thh fun?

Just thinking a bit more about the Baillie hypothesis, and also Jim G’s comment (#6) above, it doesn’t follow that we are looking for one event or type of causation, nor should we assume that discovery of a volcanic influence disproves a cometry cause, since the latter would not necessarily leave a crater or impact zone. For example, one might consider a combination of vulcanicity and a major cometry burst, somewhere in the upper atmosphere, the latter leaving a large quantity of dust or volatiles (maybe including SO2?) to be circulated in the stratosphere.

Regarding Edward G’s comment (#10 above), Edward, are you thinking of the eruption of Thera (now called Santorini) when you refer to an island in the Mediterranean? If so, I think the date for that has been fixed pretty well at about 1550 B.C. or thereabouts, so the dates do not match for this as a cause (1550 BC vs 536 AD). Do you know of any other Med. eruptions around 540 AD, as there are a number of other possible culprits, otherwise we shall probably have to look farther afield (e.g. Krakatoa, or maybe something in the southern hemisphere?).

For a broad overview of reconstructing past climates, including creating an accurate chronology and how the different proxies are combined with models, see:
Walker M and Lowe J (2007) Quaternary science 2007: a 50-year retrospective. Journal of the Geological Society, London, vol 164, pp. 1073-1092.

We are nearly at the stage of having annual climate and environmental data over the last few thousand years and extending into prehistory. Events such as volcanic explosions are very useful for correlating different climate proxies. Written records are an under-exploited source of past climate information, in my opinion.

To jbroon: Lovelock emphasises the worst possible outcome. The main reason for doubting more mild forecasts of climate change is that they fail to adequately consider feedback mechanisms (tipping points). A recent assessment of the dangers of specific tipping elements in the climate system is:
T. M. Lenton, H. Held, E. Kriegler, J. W. Hall, W. Lucht, S.
Rahmstorf, H. J. Schellnhuber (2007) Tipping elements in the earth system. ICESM Abstracts, Vol. 1, ICESM2007-A-00032.
(Tim Lenton has worked with James Lovelock and Stefan Rahmstorf is a contributor to a certain climate blog.)

Lovelock’s worst case scenario is definitely possible, but by no means certain, and while he may turn out to be right about the broad outcome, I for one do not agree with his views on energy and agriculture. For instance, nuclear power will obviously be part of the world’s future energy mix, but the expansion required to cover all our future needs is unlikely and risky in its own right, whatever the drawbacks of lifestyle change and renewable energy. It would also probably be fair to say that he enjoys scaring the cccp out of hapless interviewers, and it is easy to forget how widespread is the requirement on paid scientists to speak in measured terms or risk their job. James Hansen, because of his senior scientific post, can speak out while only running the risk of contradicting political bosses (who can’t argue with him on the science) as opposed to scientific superiors who might take a different view from him and cut off his grant money.

In the UK, politicians are examining whether to increase the 2050 emissions cut target from 60% to 80-90%, so the Hansen view of the science is filtering through.

#13 Pete Best, having read much of Hansen’s published work and all of Lovelock’s Revenge of Gaia, I really don’t see Hansen and Lovelock’s alarm as being about the same consequences. Lovelock is much more pessimistic.

#17 Slioch, Lovelock’s fear now is that what is coming will be so massive we (in the UK) must be as self-sufficient as possible. He’s quite clear about his reasons in the article, and if he’s right about what’s coming it makes strategic sense.

I don’t know what to make of Lovelock, I think he’s probably overestimated the impact. But his top down arguments appeal to the electronics graduate in me, my fear is “For want of a nail” type cascades. I hope people in 2100 will be able to look back and say “It could have been worse, just look at 536AD.”

On the subject of Lovelock’s interview, a couple of thoughts come to mind. One, a person should have more modesty than to dismiss the thoughts of someone with one of the world’s greatest minds. Second, one shouldn’t expect too much consistency in a topic as complex as climate change.

Besides, Lovelock doesn’t argue that renewables wouldn’t be beneficial, rather that they’re not practical because of the enormous manufacturing and construction effort required for them, compared to their output. Elsewhere he has pointed out that their part-time nature requires that backup energy be available. So one supposes that if the backup energy were environmentally sound there’d be no point in having the renewables.

My own view is different, but I’d hesitate to disagree with Dr. Lovelock. I think it will take a mix of renewables and nuclear to minimize the problem.

Abstract: Ruddiman ( 2003) proposed that late Holocene anthropogenic intervention caused CH4 and CO2 increases that kept climate from cooling and that preindustrial pandemics caused CO2 decreases and a small cooling. Every aspect of this early anthropogenic hypothesis has been challenged: the timescale, the issue of stage 11 as a better analog, the ability of human activities to account for the gas anomalies, and the impact of the pandemics. This review finds that the late Holocene gas trends are anomalous in all ice timescales; greenhouse gases decreased during the closest stage 11 insolation analog; disproportionate biomass burning and rice irrigation can explain the methane anomaly; and pandemics explain half of the CO2 decrease since 1000 years ago. Only similar to 25% of the CO2 anomaly can, however, be explained by carbon from early deforestation. The remainder must have come from climate system feedbacks, including a Holocene ocean that remained anomalously warm because of anthropogenic intervention.

In the late 1970s and early 1980s, there were many speculations that a full-scale nuclear exchange would create a “nuclear winter” – but the science at the time relied on simple models, and aerosol effects were poorly understood, so there were many unanswered questions. For a modern take on the question (which is similar to a volcanic eruption in some respects), see:

The modern update isn’t any more encouraging, but it does mean that the effects of aerosols, particulates like dust and smoke, are now far better understood, giving more robustness to climate model predictions.

The Pinatubo eruption of June 1991 also provided a rare modern-day test case for climate models. See:

“If you plug in volcanic eruptions, El Niños, solar variations and other natural causes and try to simulate past climate changes, you can do a pretty good job of modeling climate change until the end of the 19th Century,” the researcher said.

After that period, he said, natural causes alone don’t account for the amount of warming, about 0.6 degrees Celsius (1.1 degrees Fahrenheit), that has taken place in the last century.

“But when you factor in Pinatubo and other eruptions along with anthropogenic (human-caused) emissions,” said the scientist, “it accounts for the observed record of climate change for the past century, including the overall warming and episodic cooling, and validates the climate models.”

Abbe Mac
Going fossil fuel cold turkey would mean economic suicide.
If you want to see misery, death and destruction, then implement
the nonsense proposed by Gore and Co.
Fortunatelly, it won’t be allowed to go that far. When people start paying through the nose for this hysteria, they’ll use their votes run ya’ll out of town.
Already with the high energy and food prices, we’re beginning to see social instability.

Re #12: Oil copanies are not going to stop providing and producing oil, nor are coal companies coal or gas copanies gas but strategic targets by governments could be set but not 120% of CO2 reductions by 2020/2030 as is being requested here.

Oil companies have an absolute financial incentive to continue driving oil ever further into scarcity. With today’s new record of $104/bbl, once can see the scarce oil is a lot more valuable than if we reduced demand by conservation.

Re: #28: Going fossil fuel cold turkey would mean economic suicide.
If you want to see misery, death and destruction, then implement
the nonsense proposed by Gore and Co.

I’m already personally “carbon positive” (or whatever is better than “carbon neutral” and I’m not going broke. The people who go broke are going to be the ones who, like my DI1K (double income, one kid ;) ) friends who likely gross north of $150K and “can’t afford” a hybrid.

Economic suicide is what people do when they persist in buying new cars that run on gasoline. Which the car companies would love people to do since we’re going to be forced to by yet another brand new car when our gasoline bill exceeds our new car payment.

ObTopic: Fascinating stuff. I remember when Pinatubo blew up and the sky slowly changed from infrequent red sunsets to the far more common just about every day sort of red sunsets. I’ve been waiting ever since for “Red sky in morning, sailors take warning. Red sky at night, sailors delight” to have some manner of predictive ability.

#28 I dont think cold turkey on fossil fuel is even remotely feasible within a 30-50 year span, but Gore wasnt advocating that – rather a whole series of small measures which together bring down CO2. You can use your votes to live in a pretend-world where global warming isnt happening but that wont stop temperatures rising. Can we put your country down for say 2 million refugees? You think anti-CO2 measures will cause instability but that nothing on what climate change will bring. Oh, and every natural cycle is still working bringing ups and downs with it. Will you scream global warming has stopped with cycle or look at the long term trend? Note also the prediction that 2007, 2008 would be steady (and thats without the La Nina) but 2009 would see business as usual.

I have heard of the Krakatoa theory accounting for the 536 eruption. In his book “Krakatoa”, Simon Winchester used anecdotal evidence to claim that there was an eruption of the devilish island that helped the peasants of Sumatra overthrow their abusive rulers. Winchester then used the 1883 to help account for the overthrow of the Dutch in Indonesia and the rise of Islam in the region to its current. Its a very interesting read if you are not familiar with geology.

RE Lovelock & wind power. He lives out in the countryside, where they are proposing to build massive wind farms, which would destroy the view & kill birds. I think Robert Kennedy Jr (with Natural Resource Defense Council) is also opposed to wind for the same reasons.

As one on 100% wind I do feel a bit guilty that birds get killed and my power source may be ruining someone’s country view out in West Texas.

Maybe over time inventors will come up with wind and solar solutions that are smaller and less obstructing, ones households could employ to generate all their electrical needs (which could be reduced through efficiency/conservation measures, green building, passive solar, etc), and also use that electricity for recharging their EV or compressed air EV, so they could drive on the wind or the sun. That would mean living off-the-grid, freedom from the matrix.

Oh yes, I forgot, we’re already there. The tech is available.

Now, if we could just get the government to cut back on those huge subsidies and tax breaks to oil and coal….which we pay for on April 15th, regardless of whether we’re off the grid and driving on wind/solar power.

#24: Linus Pauling was one of the 20th century’s finest. Two Nobels in his own right (granted one not for science), and a whisker away from another with the DNA structure. Yet in later life he was plain wrong about vitamin C – to the point of nutty – though his standing meant that many assumed otherwise (some still do!).

Lovelock is wrong about nuclear and wrong about renewables. He misses the power of distributed generation. Photovoltaics on every roof and a grid extending across time zones are all that’s needed. Do-able now and affordable now. Four decades (to 2050) will be more than enough to get it done.

I’ve read the book Catastrophe by David Keys. The central theme is the 535-536 AD event was a volcanic eruption. Keys’ conclusion, based partly on local evidence, is that the culprit was Krakatua, and the 535-536AD eruption was more severe than the 18th century one.

Re. 3. Lovelock is a defeatist, although he claims to be an optimist. He does tend to blow his own trumpet – he attributes himself more prescience than I think is warrented. And it’s all very well for him to “Enjoy life while [he] can”. He’s 88.

On the other hand, I’m a pessimist. I doubt we’ll adequately deal with global warming before it starts to hurt, at which point more and greater pain is inevitable. In this case the cost will be huge, but saying we’ll be reduced to a single “breeding pair in the arctic” is delusional.

Yet I believe that it is possible for us to avoid the worst, although some effects of climate change are now inevitable. I just don’t believe we’ll do it – too many vested interests. However, I’m determined to do my bit to help minimise the damage.

Re 9 The list of major eruptions in the alst 12,000 years is clearly incomplete. Half occur after 1000AD and 25% after 1800AD. It’s very easy to image a few VEI 7s (i.e. Tambora-sized eruptions) being missed.

Pierre Gosselin claims that trying to address global warming (GW) can only be done cold turkey? Get real. NO one, and I mean NO major scientist or Government or major agency has ever claimed that we must go cold turkey on all oil/coal power sources to solve GW. So what is the person’s point besides stupid alarmism to attack other peoples ideas? Yes, there is a range of options that people propose, some more aggressive then others but none even remotely that extreme but to make a false straw man to attack GW and other people’s thoughtful idea’s is a typical, immature response to an otherwise intelligent forum.

For all the latest info on volcanos and tours to them: GO: http://www.volcanodiscovery.com. Lots of useful info here. If you happen to have a few grand in spare change, a tour to a volcano would be a really nice alternative to the standard vacation to tropical resorts. Be prepared to rough it, however. The tours go out to the volcano where you camp out for 4-5 days while you explore the volcano and hike around the area.

What’s really interesting is the list of active volcanos. Pretty scary since any one of them could undergo a major eruption, like The Son of Krakatoa.

Re: Abbe Mac..it’s true what Pierre says that suddenly going cold turkey will be economic suicide. We cant go cold turkey anyway..the infrastructure just isn’t there and wont be for decades. We can’t even decide upon a tough carbon trading scheme. We are still stuck in the committe level of progress. Logically I share your sentiments but I also realise that I must do my level best as well- I’ve got a 2 year old son who deserves a decent future. Either way our ship has reached the other reaches of one hell of a hurricane..a ‘perfect storm’ whether we come out the other side or not depends on our united stewardship..not many disparate captains pulling the ship in all directions. We have to realise also that whatever we do to mitigate CC we will still get sucked helplessly towards the eye of the storm..it’s going to get progressively worse and worse for a hundred years or more and the oceans for another thousand plus.. What we do need ‘NOW’ is definite emmission goals set by every country. I believe the world bank will have to compensate poorer countries to meet their short/medium and long term goals. We must also allow flexibily in those goals as well..as more up to date reports in the future from the IPCC and other bodies saying we must do more to but the brakes on..this must be heeded by world govs to bring forward their goals…there is going to be an enormous economic cost..not too many are denying that..but what’s the point of maintaining a robust economy if the world’s dying?

13: I personally thought Lovelocks predictions 2020 and 2040 to be beyond the pale doomster stuff. I think I understand Hansen, and I don’t think he says that post tipping point feedbacks would be anything near that rapid. Hansen is more concerned with what will happen in say 50 to a few hundred years.

I don’t think we are looking for a super-eruption. My understanding of the term is that supereruptions are Yellowstone or Toba sized events involving roughly 1000 KM**3 magma. The world probably only sees a supereruption about once per hundred thousand years. 536, is probably much less significant.

Why does the presence of sulfates rule out impacts (iceballs or hardballs)? I mean I understand reasonably well enough that volcanic eruptions produce sulfur compounds that would show up in the ice cores. But why couldn’t an impact produce the same compounds? Massive fires of either peat or forests resulting from an impact would seem to create similar releases of sulfur. From the massive fires over Indonesia recently – we saw the impact of that on the atmosphere.

I’m not questioning the conclusion – purely interest on my part. I’ve always had a passing interest in the time period – from Arthurian legends, collapse of civilization, Plague of Justinian, etc. And so whether or not the critical event of 535-6 was a comet or volcano would seem interesting – I’ve always been fond of the theory that a comet struck Western Europe.